Electric control device and electrolytic fluid therefor



March 2, 1954 c. H. RAY ET AL ELECTRIC CONTROL DEVICE AND ELECTROLYTIC FLUID THEREFOR Filed July 51, 1951 2 Sheets-Sheet l INV 0R5 CHARLES H, 3 Y BYWPH N25542:;

ATTOR EY March 2, 1954 c, H, RAY ET AL 2,671,153

ELECTRIC CONTROL DEVICE AND ELECTROLYTIC FLUID THEREFOR Filed July 51, 1951 2 Sheets-Sheet 2 INVENTOR$ CHARLES H. RA Y By JQSEPH SEA RS A TTOR/VE Y Patented Mar. 2, 1954 EnEoTRIo ooN-moL DEVICEELECL TROLYTIC FLUID THEREFOR Charles; H; Ray, Alameda,

and" Joseph Sears;

Sacramento, Galifi.,.assignors t'o Lindbergi'ImstrumentCo Berkeley,- Calif.,=a corporation 01 California Application J 111F331; 1951 SeriafNb: 239,532" 8 Gl'aims'. (Cl.-201-'-57)' This: imv'enti'on relates to an improvedlelectric control device of the-typev employing a liquid cu'r rent-modulating Ine'diumi Sucha control device may" be used in a phonograph pick-up or ma microphone or iii-any other instrument-thatis use'd to modulate electric current in accordance with mechanical-motion; sound vibrations; and the-like:

In' tlie type of electric control device to which is-invention relates; two or more chambers; e'ach containing an electrode and' a liquid that will conduct electricity, areconnected by one or more variable areaorificesi An electrical p'oten tial is impressed between the electrode in one chamber and the electrode in another chamber. Then when eXterna-lforcesvary the areaof the orifice between" them, the totalelectrical resistahce to the electrical current flowing throughthe orifibeis similarly' varied. By this'means a" signal set up external mechanical forces can be faithfully, reproduced" electrically with corresponding frequency and" amplitude characteristics. For example, a phonograph needle rerlowing a record. groove may be connected rigidly to an actuator arm having means to vary the area of th orifice and thereby set upvoltage variations corresponding in frequency and amplitude characteristicsto the-recordgroovet 'Ihisvoltage may be transmitted, amplified, and usedto con'-' trol the soundenergy ofa loud speaker, giving a faithful reproduction. of the original recording. The present invention solves certain problems that have occurred -in-such: control devicesw One problem has been the building: up of gas inside the electrode chambers; These chambers are: usually sealed oil? by a: fiexiblerrubber diaphragm which overlies-a trough or gap" in the wall between two adjacent chambers'and cooper ates: with the: partition and the gap to for-m a variable-area.- orifice. In the-past; gas has: built up inside theachambers and has distendedand' bulged th diaphragmt This:.bulging. has, iniitself, disturbed the response of thekdevice: Insome cases enough gashas built up mama-the diaphragmloose from theachamber wallisorthe liquid has spilledor has? been exposed so it can evaporate freely. The present: invention. has" solved this problem by a novel combination-of elements that prevents gas from forming to any harmful extent.

Anotherrela'ted problem has: been. the tendency of: the liquid to evaporate through the pores of thez rubber" diaphragm. When: evaporation reduced the: volume or the:- liquid-3' the: diaphragm .1

would 'be caused to lay in: the trough" orgap to siich an: extent as to out off the current: flow through the gap. The present invention-solves this problem by providing a liquid medium that does not readily evaporate.

Ahother problem has been-- the buildihg up of excessive ionization in one" chamber and a de ficienc'y of ions-m another chamber occurred because the orificesb'etweenchambers have preferably been 'kept' smalli ordertoget greater ou'tput from less='mechahicalactuatioifof th -diaphragm. The result -of uneven'-ibnization hasbe'elia severe iedlidliiiill' of output; dl'1 t'd*- a largeincrease in resistance 1 heriegativ'elcatl'i' ode) cell. In phonographs this-has tended tdre duce the volume-to e.- uselesslysxiiall amount-5 A-further problem has been" the-'formati'on'of oxides andother undesirable coating on them: ode. These coatings have act'ed as electi-icabin sulatorsand 'havetendedi to out down the-current fio'w. many cases the-entireanode haste: comecovered with this" insulating-chafing, and the urrent new has ceased-altogether:

'rhe-two last named problems"havebeefifsolved by a novel combination of electrodes; electrolyte; and liquid -medium'and by an initial concentration of the ionizihgagent irrthe"cathodeehambef far in excess of the "concentration" the: anode chamber;

7 Still anotherproblemsolved by theiiiventib'fi 1 has .beemth'e procluctib'ri ora unit Having a'relati'velyi' o'ng"and'predictableflifelwhich maybesm slfanliiallycfi extensivewith thelife '(if l'lh ile edl s0" thatthe greatest "advantage may be-taken' oi needleshaving along life. The invention makes feasible the permanent mountingofthe need-ldn the cartridge instead of having. to provide asocket', set-screw,.etc., to receiv theneedlea means that the mass-of-v the actuating arm of the pickup can be reducedto aminimum; therebyinsuring. maximum-tracking: ability' and-minimum distortion. It also preven s tampering; so that no one can change the orientation of the rfeedle and-thereby damagetherecords-andshortenthe useful life of t-he needle;

A-= turthen. problem-solved by the-invention is theprotection of the rubber diaphragms tf om harmful:- chem-icaL-actiom-bythe electrodes:

Still other objects 'andzadvantages 01 the mven tion: will: become apparent from the fdllowiiig de scriptionof a"- preferred embodiment -whichiwill be: discussedvin connection wit a pho'iii'o'grlap'h ilm piclcupr that exemplifies control device empldy ingrqthei iiveritionz The invent'ion limited to s'ucl-i use no-r t'cfi the other tures' thatare give pee creat nyway of examplem order to comply with the statute. The scope of the invention is defined by the appended claims.

In the drawings:

Fig. 1 is an enlarged isometric view of a phonographic pickup cartridge embodying the principles of the invention.

Fig. 2 is an isometric view similar to Fig. 1 showing the cartridge with the upper protective cover removed.

Fig. 3 is an enlarged isometric view partly in section taken generally on the line 3-3 of Fig. 2 with some portions cut away to show the needle mounted on the front end of the actuator arm.

Fig. 4 is an isometric view similar to Fig. 2 of the body member of the cartridge, with the diaphragm and the actuator arm removed to show the chambers and the electrodes and the liquid therein.

Fig. 5 is a view in elevation and in section taken along the line 5-5 of Figs. 2 and 4.

Fig. 6 is a view in perspective of one of the outer electrodes; and

Fig. 7 is a view in perspective of the center electrode.

The invention will be better understood from a. specific example, and for this reason a phonograph pickup employing the invention will first be briefly described, with reference to the drawings. Fig. 1 shows a pickup l having a body member H and a protective cover member l2, both made from an electrical insulating material, such as a moldable plastic. The body member is recessed (see Figs. 4 and to provide three cavities or chambers l3, l4 and I5, separated from each other by suitable partitions |6, and I8. The partitions l1 and I8 are each formed with a small gap-like depression or trough 20, 2| which extends generally at right angles to the partition. The gap extends between the chambers 13 and I4 and the gap 2| extends between the chambers IA and I5. All the electricity passing from one chamber to another must be conducted by the liquid lying in these shallow connecting troughs.

Each chamber [3, I4, l5 has an electrode 22, 23,24 respectively, and a terminal 25, 23, 21 respectively extending outside the body The present invention is best practiced when the shape, size, and composition of these electrodes bear a certain relation, and these features will be. discussed below. The invention also involves the electrolytic fluid 3|] which is used to fill the three chambers I3, l4, l5 and to lay in the gaps 20, 2|. Its composition and disposition are discussed below.

After the three chambers (there may be two or more) have been filled with the fluid 3|), they are covered with a rubber diaphragm 3| (Figs. 2 and 5), which is cemented to the body H and to its partitions so as to seal the fiuid 3|) in the chambers. A longitudinally extending actuator arm 32 (see Figs. 2 and 3) is mounted on suitable bearing blocks 33 and 34 (see Fig. 4) so as to move normal to its longitudinal axis through a small arc in response to the lateral movement of a needle 35 secured in a chuck 36 at the lower end of the arm 32 (see Fig. 3). When the needle 35 is moved back and forth as it traverses the record groove; a pair of side lever or presser foot members 31 and 38 (Figs. 2 and 5) extending outwardly from the actuator arm 32 each alternately press down and let up on the diaphragm 3| over the gaps 20 and 2|, so that the area of the gap orifices formed by the diaphragm and the gaps is contracted or enlarged in response to the needle movement. Then when the needle 35 rotates the actuator arm 32 (Fig. 5) in a clockwise direction the lever 31 will rise so the orifice at the gap 20 will be enlarged while the lever 38 will fall so the orifice at the gap 2| will be reduced in size. When the needle 35 swings the arm 32 in the counter-clockwise direction the opposite efiect is obtained.

When an electric potential is impressed across the terminals 25 and 21, the electric current passes between the electrodes 22 and 24 by way of the orifices above the gaps 20 and 2|, and the variation in orifice size produces a corresponding variation in the voltage of the center electrode 23. This voltage signal may be drawn oil from the terminal 26, amplified, and converted to sound having the frequency and amplitude characteristics of the record groove. The many advantages of the three chamber structure have already been set forth in pending application, Serial No. 239,531, filed July 31, 1951.

The present invention concerns certain discoveries of the advantages to be obtained from a new relationship between the electrodes 22,23, 24, the chambers l3, l4, l5, and the fluid 30. It concerns electrodes made from a metal more noble than hydrogen in the electromotive series, so that the electrodes will not liberate gas from the liquid. It concerns as the electrolyte a solution of a salt or other ionizable compound of metal from the same group as the metal in the electrode. It concerns as the liquid medium in which the salt is dissolved a mixture of water and a hygroscopic fluid, in a proportion where the hygroscopicity exactly balances the evaporative tendency of the water. In addition, the combination includes the use in dilute form of an acid of a type which will react with the coating that tends to form on the electrodes and will produce a soluble product, the acid being of a type that ionizes in water to form a hydrogen or hydronium ion. The individual elements of the combination and their disposition in the device will now be discussed in detail.

The electrode metal these lead cannot be used because it also has ions lower than hydrogen in the series and therefore liberates hydrogen. and oxygen from water, and

the non metals cannot be used as electrodes because they are non-conductors. Copper and silver give very satisfactory results and arerelatively inexpensive. Alloys of two or more metals from the usable metals in the above-defined group may be employed if the gradual dissolution of the anode will not change the characteristics oi. the electrolyte. i

The selection of the metal for the electrode is affected by the selection of the electrolyte and the I foundation liquid, because when an electric current is applied, the anode will gradually dissolve,

forming a salt. In order to maintain the electrolyte with the same response characteristics, the

salt formedmust be soluble in the foundation" accesseliquid: and must have: substantially the: same characteristics as the chosen electrolyte:

The electrodes.

The: outer. electrode-122: whichsserves as the anodexis; gradually eaten away. as. the device operates, losing metal: toithe electrolytic. solution: At the same time, the-other. electrode 2 1: which serves as; the cathode accumulates metal; as: it. removes the metallic ions; from the; solution. The center electrode 23 remainssubstantiallyunaffected. For that. reason it may be madesubstantiallysmaller than ,theother'electrodes: (seerEig'. 7-); Preferably the; center electrode supported: near the; upper: level of the-fluid 38;- by a support member 40; which may be an integral part of the body H The outer electrodes 2:2, 24 are preferably; bar: shaped: as shown in-Fig. 6, to 'extendrfrom. the: bottomiof'their chambers- [33. i5? almost to the:top,. and with a rectangular section, exposing a. large surface area; Their. size: helps determine the life of the control device, and in a phonograph pickup is-lpreferably calculated to givean electrode life of about twice the normally expected life ofthe needle;

Some metals,.such as copper, if used for the electrode,would'adversely affect the rubber of the diaphragm uponprolonged contact with it. As. a. protection, this invention includes a cover member ll, 42 over: each. electrode 22,2 51 (Figs; rend 5), made'from the same plastic as the body H or from any other suitable insulating material.

The'lz'quid il ater is an essential, componentoli the liquid: in order that there be ionization of the electrolyte. The main trouble with pure water is its tendency to evaporate, even through a rubber diaphragm. When it evaporates, the liquid level drops, and electrical conduction through the orifices ceases.

Pure hygroscopic liquids. even if they would work; electrically, would be undesirable, because they gradually pull water out of the air, even. through the rubber diaphragm. This additional waterwilllift the diaphragm away from the partitions and the device will fail to operate.

The present invention uses a mixture of" water with a hygroscopic liquid; in such: proportions that itsattraction of water balances the tendency of thewater to evaporate. The liquid level then remains substantially constant.

The hygroscopic' fiuid to beusedi must be freely miscible with water and v must not cause precipi tation of'salts from the electrolytic solution used. Among satisfactory liquidsarea number of-glycols, diols, glycol ethers, and amines.

Such glycols, for example, as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol and dipropylene glycol are satisfactory. As an example of a balanced solution, a mixture of about 23% water with approximately 77% ethylene glycol has proven satisfactory.

Among the satisfactory diols are pentanediol-IZ, 4, Z-ethylhexanediol-l, 3, and 2-methylpentanediol-2, 4.

Among the satisfactory amines are diethylamine, isopropylamine, ethylenediamine, diethyl-- enetriamine, triethylenetetraamine, and triethanolamine.

To prevent the formation of an oxide coating on the electrode, a small trace of acid may be added to the above liquid. For example, with copper electrodes, the addition of about one percent of sulfuric acid to 99% glycol-water mixture has proven satisfactory. Other acids, such as nitricacid; that attack'suchcoatings may paused; and no gas will be formed thereby; provided the: acid liberates hydrogen ions or hydroniumions in the electrolytic solution. Anacidshould be chosen that formsa soluble salt with the met'al used in the electrodes.

The electrolyte The electrolyte is: preferably. a solution of a. saltor other ionizable compound of a metal more noble than hydrogena. It must-be ionizablerinz water andrelatively soluble in the: mixture: of: water, the hygroscopic liquid, and: theselectedi acid. By compounding the electrolytefrom one or more metals from the same class usedrin; the. electrodes, the response characteristics or; the electrolytereinain substantially constant for the life of. the; cartridge. As the anode 2 2 dissolves; the cathode z t-builds up The amountand type of electrolyte remain constant,- and the number. of ions (and therefore the electricalconductiv-ityof thefluid): remains substantially; constant over the life of the cartridge.

Copper sulfate is asuitable salt for'the electro-- lyte. Scare other copper salts, suchas copper nitrate and copper cyanide. Where silver is the electrode metal, silver nitrate or silver cyanidemay be used.

Just as the electrodemay bean alloy of copper' and silver, for example, so the electrolytemay be a solution of a mixture ofsalts, such as-copper. ni trate and silver nitrate.

To prevent the exhaustion of metallic: ions: from the cathode chamber l5 andthe resultant; drop in output, a large excess of the electro-- lytic salt may be provided in the chamberv t5: before the diaphragm 3| is sealed to the body II. Generally, as the ions plate onto and become part of the cathode 24, the concentration. of salt in the cathode chamber l5; decreases Atthe same time, the dissolving ot the anode: 2-2. increases the concentration of salt in the anode: chamber l3.

One convenient way to assure an excess of" the:

electrolytic salt in the cathode chamber I5 is to pack into it crystals 45- of the electrolytic salt (e. g; copper sulfate crystals); The chambers I3 and Ill and the remaining space in the chamber I5- may then be filled with the fluidififl,

' which is a solution of the electrolyte in the foundation liquid, and the-diaphragm 3i is-then: sealed-in place.

Operation The. terminals 25 and 27 are connected. to a source of direct current, sothat electrons flowthrough the fluid 38 from the anode 22 to the cathode 24, via the gaps 2t and 2!. Metallic ions leave the anode 22 and disappear in the solution, and metal from the solution is deposited on the cathode 24. This occurs without the formation of gas, because the metallic base of the electrolytic salt and the electrode metal are more noble than hydrogen. The excess salt 45 in the chamber I5 supplies ions to the cathode 24 and prevents an ion deficiency even after prolonged operation. If desired, the terminals 25, 27 may be reversed after a few months of use, and the life of the unit prolonged.

The output voltage is drawn off from the center electrode 23 through the terminal 26, which remains substantially unaiiected by the ion transfer going on between the anode and the cathode.

Since the liquid 30 is balanced, its tendency to evaporate substantially equals its hygroscopic tendencies, so the liquid level will remain substantially constant.

The result of the foregoing discoveries and their application has been to make practical this type of electric pickup and to solve one of the problems which has held back its general use.

What is claimed is:

1. An electrically conductive liquid adapted to be enclosed in an electric control device, comprising a solution of a suitable electrolyte in a mixture of water and a hygroscopic liquid, the evaporative tendency thereof being balanced by its hygroscopicity.

2. The liquid of claim 1 in which there is a small amount of an acid of the type that releases hydronium or hydrogen ions in the liquid and attacks oxides of metals more noble than hydrogen to form a salt soluble in said liquid.

3. A control device for electric circuits, including in combination a body of insulating material having a plurality of chambers therein with successive chambers joined by orifices each having a variable area; means for varying said orifices; and an electrode in each said chamber and having terminal connections outside said body, one said electrode acting as a cathode and another said electrode acting as an anode; an electrolytic liquid in said chambers, said liquid being a saturated solution of an electrolytic compound; and a solid deposit of said electrolytic compound in the chamber whose electrode acts as the cathode, whereby as the metal ions tend to be depleted from the cathode chamber, they are replenished by some of said deposits going into solution, so that the electrical characteristics of said liquid remain constant over a long period of time.

4. A control device for electric circuits, including in combination a body of insulating material having a plurality of chambers therein with successive chambers joined by orifices each having a variable area; means for varying said orifices; an electrode in each said chamber and having terminal connections outside said body; and an electrolytic liquid in said chambers, said liquid being a solution of an electrolyte in a mixture of water and a hygroscopic liquid in such a proportion that the tendency of water to evaporate is balanced by the hygroscopicity.

5. A control device for electric circuits, including in combination a body of insulating material having a plurality of chambers therein with successive chambers joined by orifices each having a variable area; means for varying said orifices; an electrode in each said chamber with terminal connections outside said body; and an electrolytic liquid in said chambers containing a small proportion of an acid that reacts with the coating that tends to form on the electrode when immersed in the electrolytic liquid, said reaction producing a compound soluble in said liquid, said acid being of the type that liberates hydrogen or hydronium ions in said liquid.

6. A control device for electric circuits, including in combination a body of insulating material having a plurality of chambers therein with successive chambers joined by orifices each having a variable area; an electrolytic liquid in said chambers; an electrode in each said chamber and having terminal connections outside said chamber; means for varying said orifices; and insulated means for protecting said oriflce- -varying means placed between said orifice varying means and any electrodes that might otherwise come into contact with said orifice-varying means.

7. A control device for electric circuits, including in combination a body of insulating material having a plurality of chambers therein; a flexible diaphragm covering said chambers and helping to provide orifices joining successive chambers; electrolytic fluid in said chambers; electrodes in some of said chambers extending substantially the full height of said chambers so as to expose a large surface area to said fluid; and insulating protective means separating said diaphragm from each said electrode.

8. In an electric control device, means defining at least two enclosures electrically insulated from each other, means defining a liquid path between the enclosures; exterior means for varying the dimensions of said path; means for impressing an electrical potential between said enclosures and through the liquid contained in said path, said liquid comprising a solution of a metal that stands higher than hydrogen in the electromotive series in a mixture of water and a hygroscopic liquid in such proportion that the hygroscopicity balances the waters evaporative' tendency.

CHARLES H. RAY. JOSEPH N. SEARS.

References Cited in the file of this patent UNITED STATES PATENTS 

